Pathological features of asbestos (1332214) associated diseases of the lung and pleural cavities are reviewed. A brief history is given of the development of uses for asbestos and the growing awareness of the dangers of asbestosis during the 20th century. Occupational and nonoccupational exposure to asbestos is considered, and the mineralogy of asbestos is discussed. The appearance and detection of the asbestos body (the asbestos fiber coated with proteins and iron compounds) in tissue is examined. Long term exposure to asbestos may result in disease that is restricted to the pleura or the pulmonary parenchyma, although lesions of varying severity commonly are present in both anatomic locations. Asbestosis is pulmonary fibrosis. Gross and microscopic features of asbestosis are described. The minimal features that permit the diagnosis are the demonstration of discrete foci of fibrosis in the walls of respiratory bronchioles associated with accumulations of asbestos bodies. Assay techniques for demonstration of asbestos bodies in lung tissue are considered. Methods for pathologic study, including postmortem studies, lung biopsy, and sputum and lavage examination, are discussed. Clinical, roentgenographic, and physiological features of asbestosis are described. Malignant mesotheliomas of the pleura and peritoneum are either exceptionally rare or never occur in persons not exposed to asbestos. Development of mesotheliomas, the form of the tumor, microscopic patterns, and diagnosis are discussed. Association of carcinoma of the lung with asbestos exposure has also been established conclusively. The pathogenic importance of various types of asbestos and host factors in asbestosis are considered. Methods for the assessment of lung fiber concentrations, pathologic grading of asbestosis, and preliminary evaluation of the grading schema are discussed in appendices.